What diameter do I cut around stg 1 valves?

I saw a post some time back where a meaurement was given for deshrouding stg 1 valves. can't find it. what diameter works at what depth. I will probably rough in a small amount with the bridge port at work to get some consistancy across the chambers. Then work them in when I polish the bowls. I'm having the valve job done after I polish the bowls .

I have lathe and milling experiance from making and modifying many a part for work... but have never done any head work. this will be a learning experiance.

Any advice and/or tip would be great.

BTW: These are 71 castings I'm converting to stg 1.




:3gears:

 

Go direct to the man

http://www.gesslerheadporting.com/

 

Gregs the man most definatally. Not sure that it would be polite to ask him for such info, without using his services.

However I did take a peek at his site and got an idea of what he was doing with the fly cutter. It apeared that the he was fly cutting the relief in the combustinon chamber some where near the edge of the cylinder line.

Should I scribe a line on the head with the head on the block, indicate the center of the seat, and fly cut the to the line with whatever radius that is? OR, should I cut a few thou short of this and then round the edges slightly to reduce detonation?(not sure if the sharp edge would be a problem at the out side edge of the chamber)
o No:

 

ttt

 

It is best to use the block to draw your circle. Cut out near the line and then round off the edges.

I usually just use a die grinder and cut from the line down to the valve seat at an angle. This may not work best but it is the only tool that I have for the job.

Hope this helps. Also did you see this?


http://www.gesslerheadporting.com/m...6dd80023623d/b6272214d1bc772285256e1a0004e725

 

Thanks Jimmy, I saw that from your previous link. Looks like that'll be what I do. Had a talk with my machinist and found out that he has accuired a Serdi valve machine. He said he could cut them while I'm still figuring how to set it up on up on the Bridgeport!
He has a selection of different profile tool bits, and a really trick head tilt head. He said bring them to him two weeks from now. I'll start ruffing in the ports while I wait. I have have most of my measurments from my port molds(I'll post pix in a while), and I'm figuring my square inches of crosectional area. Think I'll do some more Smoky (Yunick) reading tonight. I'm not going real elaborate or thin with the ports. Just want to make some well thought out cuts in some key areas to get the basics. Then I'll spend some time polishing ports and combustion chambers and make damn sure they are the same.

Which brings me to the next herdle. Ugly reverse pockets on 3-6 exaust. Need filled(still). Machinist has no time just to set this up for one pair of heads. If he had enough time or had a few to do, he would. busy guy(doesn't even advertise at all). a buddy at work has a small foundry set up. I'll take him the heads tommarrow to show him what I want. I'm thinking aluminum. Need to look through my crappy piston collection.
:laugh:

 

Port mold pix

Here is an exhaust port.

 

port mold pix

here is an Intake...

 

port mold pix

This is probably the same thing that a few online supply houses have selling for port mold compound. this is a liquid latex rubber mold compound I found at the local hobby shop for ten bills.

 

I use this stuff called blue sel its real easy to use and you just smear some vasaline in the port for release agent.

 

I just used cheap penatrant. were did you get your stuff?

 

Is this useful?

http://64.32.210.122/Cars/71GS/Engine/index.html

 

YES. Very Cool. Did you take these? Nice large pictures. Thank You

 

Actually, I just put the parts right on the scanner.

 

Those are really cool pictures Bill

I've never messed with trying to port heads myself, and I probably never will. But that doesn't stop me from being interested in the process.
Could anyone shed some light on where the biggest "flaws" in port design are in those pics? By that, I mean what would be the first thing you would start grinding on in those pics?
Thanks
:TU:

 

Valve guides and pocket are the most restrictive. cutting elswere won't so much for ya until tese restrictions are reduced.

 

Are Bills picture "before" or "after" porting?
I know what the valve guide is. What are you calling the "pocket"?

I can see where the port is the thinnest, but it doesn't look like you could take much meat out without breaking into the (water pockets?)

Thanks
:beer

 

Well you hit it right on the head, that's the big trick. here is a shot of a port mold(intake) of the same '71 head.

this shot shows how large the valve guide is(it needs reduced quit a bit

 

this shot shows how the guide takes up half of the pocket.